1. Field of the Invention
The present invention generally relates to an active device capable of converting an electrical signal into a voltage, more specifically, to a magnetic recording head consisting of either an anisotropic magneto-resistive (hereinafter referred as AMR) or giant magneto-resistive (hereafter referred as GMR) sensor along with an insulation spacer and magnetic shields.
2. Description of the Related Art
As is well known in the field, the insulating spacer in AMR/GMR recording heads is becoming thinner and thinner in order to increase a linear recording density. Inevitably, we are facing electric-pop noise resulting from the thinner spacer. For high manufacturing yield and reliability of electric and magnetic performance, such electric-pop noise must be eliminated.
U.S. Pat. No. 3,864,751 entitled “Induced Bias Magneto-resistive Read Transducer” issued to Beaulier and Napela, on Feb. 4, 1975 proposed that a soft-adjacent magnetic transverse bias layer (hereinafter referred to as “SAL”) is isolated from a magneto-resistive device (referred to as “MR” hereinafter). The patent did not reveal any methods how to make it. Another key point is that the MR and SAL are electrically isolated. In the prior art described by Beaulieu et al., electric-pop noise is present if a thinner insulating spacer (<150 Å), such as Al2O3, is used. Otherwise, the devices would need a thicker SAL to bias the MR if a thicker insulator spacer (2-400 Å) were used. There are two problems associated with the latter case. Firstly, the SAL can not be easily saturated by a current in the MR and an antiferromagnetic pinning layer must be used to pin the SAL so that the SAL magnetization is perpendicular to the current direction. In this case, the device process becomes very complicated and it also renders designs less extendible to a narrower shield to shield spacing for higher density recording.
The SAL has a function as a shunt bias layer in SAL biased AMR devices. When the MR and SAL are spaced by electric conducting materials, such as Ta, the SAL and MR devices have the same electric track width. These configurations have been disclosed in U.S. Pat. No. 4,663,685 issued in 1987, to C. Tsang, U.S. Pat. No. 4,639,806 issued in 1987 to T. Kira, T. Miyagachi, and U.S. Pat. No. 5,108,037 issued to M. Yoshikawa, M. T. Krounbi, O. Voegeli and P. Wang.